More people will be banking on their mobile phones and tablets than online within five years, Westpac group executive, retail and business banking, Jason Yetton says.

Mr Yetton said the explosive growth in mobile banking over the past two years, with more than 1.58 million Westpac customers using their devices for transactions, will accelerate.

Westpac estimates that the number of payments made across its digital platforms will exceed one billion transactions within five years, with a total value of $6.8 trillion.

Of these, Westpac expects its mobile customers to increase to 5.2 million and online customers to five million by 2017/18.

"Our experience is that the take-up of mobile banking is much faster than any previous technological innovation in banking," said Mr Yetton.

"Over the next five years we expect the gap between online and mobile to narrow sharply with active mobile and online users each reaching the five million mark and mobile overtaking online users in 2017-18."

In 2011, around 960,000 customers were actively banking with Westpac using their smart phones and tablets, compared to 3.1 million accessing their accounts online.

Mr Yetton said within a year those numbers have grown to 1.58 million for mobile banking and 3.4 million for online.